Process and apparatus for the refining of pulp



Sept 3, 1935. A v c. B. THORNE 2,013,115

PROCESS AND APPARATUS FOR THE REFINING OF PULP Filed Sept. 21, 1931 2 Sheets-Sheet 1 i; g m.

INVENTOR; CARL B. THORNE.

ATTORN Eys.

Sept. 3, 1935. c. B. THORNE 2,013,115

PROCESS AND APPARATUS FOR THE REFINING OF PULP Filed Sept. 21, 1951 2 Sheets-Sheet 2 INVENTOR CAEL B. THORNE.

ATTORNEY5.

Patented Sept. 3, 1935 UNITED STATES PROCESS AND APPARATUS FR 'llHE REFINING OF PULP Carl Busch Thorne, Hawkesbury, Untario,

Canad Application September 21, 1931, Serial No. 564,199

4 Claims.

This invention relates to the refining of pulp, particularly wood cellulose pulp, and more particularly to the use of a gaseous refining or bleaching agent.

Heretofore difllculties have prevented the commercial use of available gases for the bleaching or other refining of cellulose pulp. Chlorine gas is an eifective reagent for removing impurities ,irom pulp but its toxic character has made its large scale commercial use practically impossible in existing processes and apparatus. An object of this invention is to provide a process and apparatus for treating cellulose pulp with a gas, such as chlorine, with a view to bleaching and purifying-the pulp.

Other objects of the invention are, to provide for theuniform and thorough impregnation of the pulp with the gaseous reagent, to prevent the escape of the gas into the plant, to recover all the gas not consumed in bleaching or refining the pulp, to provide for accurate control of the flow of pulp and reagent respectively, and to provide a process and apparatus which may be operated with-relatively low power consumption. The invention also contemplates regulating the temperature of the pulp to control the reactions -on the pulp and the introduction of caustic or other alkali to neutralize acids formed and iur- I ther refine the pulp, as desired.

Referring now to the accompanying drawings, which illustrate, by way of example, several forms of apparatus for carrying out the improved process.

Figure l is a partially diagrammatic, sectional elevation of one form of apparatus;

Figure 2 is an enlarged side elevation of detail to be described later, and

Figures 3, 4, and are sectional elevations of three modified forms of the improved apparatus.

The apparatus shown in Figure 1 comprises a pulp shredder I of any convenient construction, and may be of the form described in my prior patent, No. 1,767,102. The outlet 2 of the shredder discharges into a vertical cylindrical tank 3,

, the lower portion of which is enclosed in a tower 4. V Rotatably mounted in the tank 3 and coaxial therewith is a shaft 5, driven in any suitable manner through a pulley 8 and gearing I. Rigidly mounted on the shaft 5 are suitable screw conveyors, two of which are indicated at 8 and 9, these screws being arranged to feed the pulp downwardly.

Below the conveyor 8 is a stationary spider or bar to carried by the tank 3. This spider may have a central boss. or bearing for the shaft 5 and two or more horizontal arms extending radially to the interior wall of the tank 3. Immediately below the spider ill a. comb ll is rigidly mounted on the shaft 5. The comb comprises a central boss keyed to the shaft and two or more 5 radial arms having upwardly projecting teeth.

Below the comb II a combined agitator and impregnator I2 is mounted for rotation with the shaft 5. The member l2 comprises a central boss l3 having a plurality of radial hollow arms 10 it. The arms H are preferably triangular in cross section (see Figure 2) with one of the edges l5 directed forwardly with respect to the direction of rotation of the device. The rearwardly facing wall of each arm 14 is provided with a 15 series of holes l6. The shaft 5 is hollow down to the impregnating device l2 and is connected in a sealed manner at the upper end to an inlet pipe H for bleaching medium.

A discharge aperture l 8 is provided at the lower 59 end of the tank 3, and a valve I9 is provided to close the opening. For example, the valve may be caused to close automatically when the flow of pulp ceases by means of a weight or other suitable means.

Any convenient means may be provided to control the temperature of the pulp. For instance, a pipe 2| may-be provided adjacent the lower end of the tank 3 to inject heating or cooling medium of any kind, for example, hot or cold air or water, or steam, according to requirements.

The tower 4 discharges at the lower end into a conveyor 22, the discharge being governed by a rotating device 23 in a known manner.

A pipe may be provided at 24 to introduce caustic or other alkali in either a sufiicient quantity to neutralize acids formed by the preceding refining operation, or in excess for further refining the p p- The pulp is discharged from the conveyor 22 at 24 for washing and further processing.

Gas outlet pipes 25 and 26 connect the tank 4 and conveyor 22, respectively, to a suction fan 21, driven, for example, by a motor 28, which discharges into a gas reclaiming tower 28. The gas is distributed in the reclaiming tower through the nozzle 30 an'd'fllls the tower. At the bottom this tower is filled with a liquid medium suitable for absorbing the gas, this liquid being kept at a constant level by a float controlled valve II, and circulated from the bottom to the top of the tower by a pump 32. As it falls down the tower, the liquid is distributed over any suitable baiiles 33, and falls to the bottom of the tower, absorbing the gas as it does so. The liquid medium as it bebleaching medium supplied through the hollow comes saturated is led off through the pipe 34. The reclaiming tower may, for the recovery of some gases, be filled with limestone.

In order to make the apparatus safe to use, it has been. found necessary to provide means for automatically closing off the refining or bleaching medium under certain conditions. For instance, should the pulp for some reason cease to flow into the tank 3, then the refining or bleaching medium might back up and distribute itself through the system. To prevent this risk a small lever arm 35 is pivoted at the outlet of the bleach-introducing apparatus. While the pulp continues to fiow, a switch arm 36, carried by arm 35 is held in a closed position against contacts 31, but should the flow of pulp cease, then the switch arm 36 will fall, and the electrical circuit will be broken, thus de-energizing a solenoid 38 and allowing a weighted arm 39 to drop and thus close a valve 40 in the bleaching medium inlet pipe I1. Also should the electric current fail at any time, the suction fan 21 would cease to operate, and so the gas might find its way into the mill. Therefore, the solenoid 38 mentioned above, is also placed in series with the motor 28 of the fan, so that should the current fail, the bleaching medium valve will automatically close.

The pulp from the shredder I is fed downwardly in tank 3 by the conveyor 8. The spider I0 holds back the pulp to some extent and the comb I I scrapes the pulp from the mass supported by the spider. The pulp thus detached by the comb falls in the gas filled zone between the comb II and impregnator I2. The device I2 rotates through the pulp and injects into it gaseous or liquid part of shaft 5, the arms I4 and. holes I6. The pulp is thus thoroughly and uniformly impregnated with the medium. The impregnated pulp is next continuously fed downwardly by the screw 9, and passes through the outlet I 8 into the tower 4. The commencement of operation of the discharge member 23 and conveyor 22 is delayed until a suitable body of impregnated pulp has accumulated in the bottom of the tower 4. The extent or this delay will depend on the time required for the refining medium to produce the desired effect on the pulp. If this effect is obtained thirty minutes after impregnation, the discharge from the tower is initiated thirty minutes after the pulp commences to fiow into the tower. after the discharge from the tank 3 into tower 4 and the discharge from the tower into conveyor 22 are continuous. The excess gas is withdrawn from the upper end of the tower and reclaimed in the tower 29 in a manner which will be clear without further description. If any further excess gas is released from the pulp in the conveyor 22, it is drawn away for reclamation through the pipe 26.

In Figure 3 the mixing tank 3 is of slightly different constructon and is disposed horizontally outside the tower 4. The shredded pulp enters the tank 3 and is fed towards the left by the screw 0 which also forms a gas sealing means. The agitating and injecting device I2 operates as previously described, being supplied with bleaching medium through pipe I1 and the hollow part of the shaft 5. The left-hand end of the tank is preferably directed upwardly as at M to form a trap so that the tank is maintained substantially filled There-- with pulp. The outlet 42 of the tank discharges into the tower 4, and at the junction of the trap 4| and the discharge 42, or at any other convenient point, a rotating comb 43 may be provided similar to the comb II shown in Figure 1. The impregnated pulp, scraped off by the comb, falls through the outlet 42 into the tower 4, in which it may fiowover a series of bafiles 44 so as to prolong its exposure in a shredded condition to the gas in the tower. The gas reclaiming and safety devices, shown in Figure 1, may, of course, be employed in connection with this modified apparatus.

In Figures 4 and 5 the pulp is introduced into a hopper 45 and fed past a gas-sealing valve 46, by a screw 41 which also forms a seal for the gas. The bleaching medium may be introduced at any suitable point, for example, between the screw 41 and valve 46 by being led through a bore in the shaft of the screw 41. The pulp, after passing the valve 46, enters a drum 48 which is rotated by any suitable means such as rollers 49. In Figure 4 the pulp is agitated by radial vanes 50 and advanced along the drum by a helical conveyor 5I. The pulp is discharged through an outlet 52 into the tower 4. In Fi ure 5 the interior of the drum 4!! has a helical series of radial vanes 53 which both agitate and advance the pulp.

It will be understood that many further modifications are possible within the scope of the appended claims.

The term gas" as used in the appended claims.

is intended to include gas per se, as well as gas combined in excess with liquid.

I claim:

1. Apparatus for refiningpulp comprising a container, pulp conveying means in the container, means for retarding the flow of pulp, a comb for scraping pulp from the retarded mass of pulp,

means for impregnating said pulp with a refin-' ing medium, a reaction chamber into which the impregnated pulp is discharged and means for discharging the pulp from said chamber after the reaction is complete.

2. In a pulp refining apparatus, a cylindrical container, a pulp inlet at one end of said container, a pulp outlet at the other end of said container, means within said container for injecting refining medium into said pulp, and a screw conveyor between said injecting means and pulp inlet for advancing the pulp towards said injecting means and for preventing the escape of gas from said inlet.

3. A pulp refining apparatus comprising in combination with a closed reaction chamber, a chamber providing a confined gas and pulp mixing zone, said second mentioned chamber having a pulp inlet and a gas-pulp mixture outlet, a screw conveyor adjacent said inlet to prevent the escape of gas therethrough and to feed pulp to said zone, means adjacent said outlet to prevent the escape of free gas therethrough, and means in said confined zone for injecting streams of gas into pulp delivered by said screw conveyor.

4. Apparatus as defined in claim 3 having means adjacent said screw conveyor for shredding the mass of pulp delivered to said confined zone by said conveyor.

CARL BUSCH THORNE. 

